Wheelchairs help those incapable to walk to move from one place to another. Conventionally, a wheelchair is driven manually by another person for moving the person seated thereon. This is generally inconvenient. An electrical wheelchair incorporates a power source, such as a battery-motor system, therein for assisting the movement of the wheelchair. The conventional wheelchairs are designed for moving on a substantially planar surface whereby turnover or other potential risk may occur when the wheelchair is moving on an uneven surface. Some of the conventional wheelchairs are equipped with tilting-resistant device for reducing the risk of tilting or turnover when moving on the uneven surface. Such tilting resistant devices are not good enough to effectively prevent the wheelchair for tilting and turnover. Some examples of the conventional wheelchairs are disclosed in U.S. Pat. Nos. 5,222,567 and 5,762,154.
Thus, it is desired to provide a wheelchair having a double-framed chassis which provides wheels thereof with excellent surface compliance when moving on an uneven surface thereby reducing the risk of turnover.